The house was built at some indeterminate date in the 18th century. One small window on the back staircase still has small panes, four in each of the pair of casements, separated by narrow glazing bars. A photograph probably taken about 1900 shows the main windows had double hung, sashes in the centre with fixed panes either side, the sash weights boxed in wooden mullions between the moving sashes and fixed sections. This is an arrangement still seen in many of the Georgian town houses in Louth such as this one in Westgate.
|
|
While the window at the side of the house had Georgian panes with 6 over 6 sashes, similar to the Westgate photo, those at the front had larger panes, eight in all with the sliding sashes divided by just one vertical glazing bar. Presumably this was a Victorian replacement of the original windows with small panes which may have already lasted over a century.
|
|
In about 1960 all were removed and replaced with particularly dull casements with the window divided into three vertical sections with three large panes, the centre fixed and casements to the side. There were three small panes above. Forty years on and the softwood sills and bottoms of jambs and mullions had rotted well beyond the point where paint could hold it all together. Time to replace them with wooden double hung sashes with twenty panes arranged as of old. And we wanted them double glazed. |
|
Replacement windows are subject to Buildings Regulations. Basically, the government in a bid to save the planet from global warming and show that it is doing its bit to reduce CO2 emissions, has said that if you are replacing your windows the new ones must have a rather low U-value. The effect is that they have to be double glazed using low-E glass (that's Pilkington-K glass since Pilkington seem to have a monopoly). The glass is 4mm thick and the gap needs to be 16mm making a sealed unit 24mm thick. Add glazing tape and beading and about 40mm of rebate are needed from front to back. The sealing strip needs to be completely covered by the rebate and beading so a width of at least 15mm is needed sideways. Double glazing is heavy so the glazing bars need to be strong. All in all, the glazing bars need to be not much less than 60mm front to back and 40mm side to side. While Queen Ann buildings often had such wide glazing bars, many Georgian windows were made with much narrower, lighter bars, carrying the then customary eighth of an inch (about 3mm) glass. Typically, Georgian bars were about 18 or 20mm wide while some as narrow as 15mm were made in the 19th century.
The Building Regulation about U-Values doesn't apply to conservation work. One could fit windows of the traditional design into an old house and if it was a listed building or in a conservation area one would probably have to.
Not everyone is convinced by the governments planet saving arguments. The cost of replacement double glazing would not be recouped by lower fuel bills for many years, perhaps a few decades. The energy used in manufacture has to be weighed against fuel saved in domestic heating. The sums rather depend on the longevity of the windows. The epidemic of plastic windows does not come with lifetime guarantees. Have you ever come across a double glazing salesman willing to offer a 50 year or century guarantee? Yet there are plenty of wooden frames that are still sound and serviceable after two centuries.
We don't really know how long plastic window frames last yet because they haven't been around long enough but it may turn out that something as non-biodegradable as u-PVC lasts less well than the eminently biodegradable wood. Much depends on the type of wood and how it is used and looked after. Most softwood commonly available these days is not classed as durable so will rot in a few years. Its use has given wooden windows are rather poor reputation. Only western red cedar, from west coast North America, and larch and Douglas fir, both grown in Britain, are durable, meaning that they could last a few decades in external joinery without the need for chemical preservatives. But even larch or Douglas fir requires painting when used for windows. And that's a whole other story. Paint used to be linseed oil and pigment. It took ages to dry but stuck to the wood without ever peeling off and just needed over-painting only after several years. Bad for decorators in a hurry and the paint industry that relies on regular sales. So they invented modern paint which dries quickly and falls off next winter.
So what happened a long time ago? Before the days of cheaply imported Scandinavian softwood, the timber of choice for external joinery was oak. Oak has some remarkable properties. It is very durable, the tannins acting as a natural preservative. No need for the modern chemicals - they wouldn't penetrate anyway. And no need even for paint. Untreated oak soon weathers to a silvery grey colour but does not rot. Look at a Tudor building and you will see oak that has remained sound for four or five centuries. No painting, no preservatives, just sensible designs which allow the timber to dry out. So what happened since a long time ago? Well, English oak gradually became scarcer and so more expensive just as Scandinavian softwood began to be imported cheaply. The joiners, in the pre-power tool era, found softwood much easier to work than the strong, hard oak. Paint, basically linseed oil and white lead, was developed to make up for the reduced durability, first being mixed up on site and later giving rise to a specialist industry. By the end of the 18th century the fashion for white painted softwood window frames was established. And it stuck. The 19th century dyestuff industry introduced a range of strong colours so the Victorians painted their windows red and brown and blue and green but white, or rather 'off-white', came back into fashion in the 20th century. 'Brilliant white' is a post-war invention.
With all that in mind it is time to consider design for the new Tithe Farm windows. Oak has the clear advantage that it lasts pretty much for ever without any need for painting. English oak that is. There is an American oak which is not so durable so don't go there. Of similar quality to English is the French, though they keep the best stuff for wine barrels, and increasingly oak is being imported from eastern Europe. But my local sawmill, Nelson Butler of Horncastle, specializes in English oak. It is comparatively expensive at between £20 and £30 per cubic foot (not a very metricated industry, this) when bought in 2 or 3 inch thick boards. And it can't all be used; the inch or so under the bark is sap wood, a slightly paler colour and is not durable. It does not contain the tannins which preserve oak so cannot be used in external joinery. And then there are various cracks and shakes which mean more wastage.
From Wood to windows
|
|
|
|
|
|
|
|
Sliding sashes traditionally involved the weight of the window being balanced by iron weights housed in wooden boxes to either side, both weights and sashes being suspended from pulleys. Our windows have a pair of sliding sashes in the centre with fixed lights either side. The traditional weight system would have required boxes that produce rather thick uprights, as seen in the picture at the top of this page. But with the thicker glazing bars needed to accommodate double glazed units we wanted to make the upright jambs thinner.
|
The answer comes in the form of a clever bit of technology called a spiral balance. This is a 16mm diameter tube containing a spring which exactly balances the weight of the sash whatever the position it is in. There is one each side of each sash, fitting into a groove cut in the solid wooden jamb. So we have thinner, stronger jambs, easier to make than a box and with no cords to replace when they break. Buy them from Balance UK Ltd. This picture shows the upper sash in place but the lower sash not yet fitted. The spiral balance is fitted into its grooves in the jamb.
|
|
Would you like some hand-made oak windows of your very own? Click on the link to Tithe Farm Oak Works.
Contact: biff@biffvernon.freeserve.co.uk
©Biff Vernon 2003
